Yingluck Shinawatra has been confirmed as Thailand's first female prime minister after winning a parliamentary vote after her resounding election win last month.
The lower house of parliament voted on Friday to elect Yingluck with 296 of the legislature's 500 members voting in her favour.
"I am excited to start work," she told reporters after the vote. "People will judge whether my work satisfies them and meets their expectations or not."
The vote came a month after Yingluck's Puea Thai party and its partners won a three-fifths parliamentary majority in the July 3 election.
Yingluck, whose political career began only 11 weeks ago, will become Thailand's 28th prime minister.
She will officially assume power after King Bhumibol Adulyadej endorses her in a separate ceremony expected within days.
Yingluck will face the immediate challenge of bringing stability to the kingdom, after five years of political turmoil since her brother Thaksin was thrown out of office in a 2006 army coup, backed by Thailand's elites.
The 44-year-old businesswoman to the post, who campaigned on a platform of national reconcilliation, must also prove she is not her brother's puppet, as critics claim.
"What she's got to do is make sure everyone is placated within her loose coalition that supported her through the election," Al Jazeera's Veronica Pedrosa, reporting from Bangkok, said.
"But at the same time she faces a virulent opposition in parliament who want to see that she was serious about the reconcilliation process that she promised during the campaign.
"They are very mistrustful of her because she is the little sister of former prime minister Thaksin Shinawatra, who many analysts say presents a profound challenge to the establishment, the elite and the military."
Described by her brother as his "clone," Yingluck surprised observers with her assured campaign style prior to the election.
"She says that she is not just a mere proxy but she is going to have to prove it," said Pedrosa.
"And it's going to be very difficult. What we are in fact seeing is a political dynasty being created; the Thaksin clan is back in power."
On Friday, Yingluck again rejected suggestions that Thaksin, who lives abroad to avoid a jail term for corruption, is controlling her party from afar.
Asked if she was in contact with her brother, she replied: "No, I am not talking to anyone."
Yingluck also faces the immediate challenge of keeping the country clear of the sometimes violent unrest it has witnessed in recent years.
She will have to navigate a complex political terrain and find a delicate equilibrium between the coup-prone army and the elite establishment on one side, and the her brother's "Red Shirt" movement on the other.
The "Red Shirts" helped vote her into office and want to action take over the bloody military crackdown that ended its protests in Bangkok last year.
Analysts say Pheu Thai's landslide victory last month boosted Thailand's prospects for stability in the short-term, but that the honeymoon may only last a few months.
They also believe a key test for Yingluck will simply be whether she can hang on to power in a country where the removal of leaders is commonplace.
Thailand has seen 18 actual or attempted military coups since it became a constitutional monarchy in 1932, and only one prime minister in that time, Thaksin, has served a full four-year term.
Yingluck's party is the latest incarnation of Thaksin's original Thai Rak Thai party, which swept elections twice before Thaksin was overthrown.
Two pro-Thaksin prime ministers who followed were removed after hostile judicial rulings and parliamentary manoeuvring that came as enraged "Yellow Shirt" demonstrators took to the streets, at one point shutting down both of Bangkok's international airports and stranding hundreds of thousands of travellers.
The "Red Shirts" have fought back, most recently by flooding central Bangkok in 2010 for two months in demonstrations that ended with more than 90 people dead and nearly 2,000 wounded.
Yingluck replaces outgoing Democrat Party Prime Minister Abhisit Vejjajiva, whose establishment-friendly party limped to a distant second in the poll.
Abhisit addressed the nation for the last time as acting prime minister on Thursday evening, defending his economic credentials and expressing hope that the move to a new government can help end political conflict in the country.